It is known that various biophenomena in a bion each show a “periodic rhythm” which vibrates in a self-supporting manner. This periodic rhythm is called “biological rhythm.” Especially, a “circadian rhythm” having a period (cycle time) of about one day governs widely the biophenomena such as the sleep-wake rhythm and diurnal variations in body temperature, blood pressure and quantities of hormones secreted. In addition, the circadian rhythm is known to relate also to mental and physical activities, capacity for locomotion, drug sensitivity, and so on.
The biological rhythm is controlled by a gene group called “clock gene.” The clock gene (which may hereinafter be referred to also as “clock molecule”) functions as a “biological clock” by autonomously periodically varying (vibrating) the expression, activity, localized presence or the like thereof. Specifically, by controlling other various kinds of gene groups, the clock gene governs the above-mentioned various biophenomena. It is considered that the biological clocks based on the clock molecules are present on a variety of levels of each of cells, tissues and organs in the living body of a bion, and the biological clocks are synchronized with each other to create the biological rhythm of the bion as a whole.
It has been clarified that gene polymorphism and gene mutation of the clock molecule would be critical causes of cancer, diabetes, vascular diseases, altered-nerve diseases and the like. In recent years, furthermore, it has been pointed out that a gene polymorphism or mutation of the clock molecule relates also to the crisis of mental disorders such as bipolar disorder and depression. In connection with this, a therapeutic method has been tried in which the biological clock having been brought out of order due to a gene polymorphism or mutation is reset by irradiation with light.
On the other hand, the sleep-wake cycle, for example, is not only autonomously controlled by the biological clock but also is under restrictions by social life. Thus, a change in the bedtime or the rising time in daily life may cause a rhythm deviation (phase deviation) between the “going-to-bed and rising cycle in real life” and the “sleep-wake cycle based on the biological clock.” Such a deviation (lag) of rhythm is considered to induce the so-called “jet lag” or somnipathy and, further, to cause the above-mentioned mental disorders.
A deviation (lag) generated between the so-called “external time” and the so-called “internal time,” such as that between the “going-to-bed and rising cycle in real life” and the “sleep-wake cycle based on the biological clock,” is deemed as an “internal desynchronization” of biological rhythm. The “internal desynchronization” can be said to be a state in which the biological clocks of organs in a living body are desynchronized. The internal desynchronization is considered to arise from the fact that the biological clocks of the organs differ from each other in readiness to get synchronous, so to speak the speed of synchronization, with the external time. It is known that when an internal desynchronization is generated, a biphasic rhythm comes to be observed in the diurnal variations of body temperature, blood pressure, etc. Attempts to maximize the effect of pharmacotherapy by utilizing the biological rhythm have begun. Due to the amount of expression of a molecule serving as a target of a drug (drug target molecule) and the circadian rhythm of an enzyme which metabolizes the drug (drug-metabolizing enzyme), the therapeutic effect of the drug is also considered to show a diurnal variation. Taking this into account, there has been proposed a way of thinking called “chronotherapy” in which maximization of a therapeutic effect is contrived by determining an optimal medication time for each drug.
Besides, in a more familiar aspect, the acting time for bringing out personal ability to the full in learning or trailing and the eating time for a person to get fat with difficulty (or with ease) have come to be investigated utilizing the circadian rhythms of mental and physical activities and capacity for locomotion.
From the foregoing, it is considered that to accurately know the biological rhythm based on a biological clock is very useful for prevention of various diseases, for improvement of poor physical condition such as jet lag, for realization of chronotherapy, for exhibition of personal ability, for a diet, and so on.
PCT Patent Publication No. WO 2004/012128 discloses at least a method for estimating a biological time on the basis of gene expression product amount measurement data on a standard specimen taken as a sample from a bion. In the biological clock estimation method, a molecular timetable for estimation of a biological clock is formed based on the expression amount of a gene expression product (specifically, mRNA). Incidentally, PCT Patent Publication No. WO 2004/012128 does not describe a specific tissue (or cell) to be taken as a sample or a specific gene to be measured.
Japanese Patent Laid-open No. Hei 6-189914 describes a biological rhythm curve measuring apparatus for measuring a biological rhythm curve from measured values of deep body temperature of a human being. In the biological rhythm curve measuring apparatus, a contrivance is made such that a true biological rhythm curve can be measured through removing influences of disturbances (external influences). Incidentally, Japanese Patent Laid-open No. Hei 6-189914 shows rectal temperature or tympanic temperature as a specific example of the deep body temperature, and describes that the rectal temperature is particularly preferable.
In addition, as inventions relating to the present invention, Japanese Patent Laid-open Nos. 2002-168860, 2006-345869, and 2006-345870 may be mentioned which each disclose a method of determining stress by using as an indicator the activity of alpha-amylase in the saliva of a subject. In the stress determination method, the activity of alpha-amylase in the “saliva” is measured, whereby the degree of stress in the subject can be determined simply and easily.
The biological clock estimation method disclosed in PCT Patent Publication No. WO 2004/012128 is a method based on the expression amount of mRNA of a standard specimen taken as a sample from a bion. While PCT Patent Publication No. WO 2004/012128 does not describe a specific tissue (or cell) to be taken as a sample or a specific gene to be measured, a method of examining the expression of a clock gene in leukocyte has hitherto been adopted widely as a simple method. In this method, however, taking a sample of blood is indispensable, which is attended by a physical pain in the subject.
Furthermore, it is necessary for the measuring person to conduct an operation of separating the leukocyte from the blood taken as a sample, an operation of extracting mRNA from the leukocyte, analysis of the expression of the clock gene mRNA and the like, which has been the reason why it take much time and labor to carry out the method. In fact, in order to extract mRNA from an organism specimen and determine the mRNA, in general, an intricate operation is needed for preventing the mRNA from being decomposed. Especially, if decomposition of mRNA occurs in dealing with a very small amount of organism specimen, it would be impossible to obtain stable measurement results.
The biological rhythm curve measuring apparatus disclosed in Japanese Patent Laid-open No. Hei 6-189914 is an apparatus for measuring particularly the rectal temperature. Measurement of body temperature in the rectum, however, imposes a mental or physical pain on the subject and, therefore, the measuring person also gets a feeling of burden.
Accordingly, it is an object of the present invention to provide a simple and low-invasive method for acquiring information about a biological rhythm of a bion.